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| author | Kevin Wolf <kwolf@redhat.com> | 2019-04-15 16:25:01 +0200 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2019-04-30 15:29:00 +0200 |
| commit | f29fbf7c6b1c9a84f6931c1c222716fbe073e6e4 (patch) | |
| tree | 10fec182079ffb17a7acdcdaf91a9c5d2b8ba01f | |
| parent | de38b5005e946aa3714963ea4c501e279e7d3666 (diff) | |
| download | qemu-f29fbf7c6b1c9a84f6931c1c222716fbe073e6e4.zip qemu-f29fbf7c6b1c9a84f6931c1c222716fbe073e6e4.tar.gz qemu-f29fbf7c6b1c9a84f6931c1c222716fbe073e6e4.tar.bz2 | |
qcow2: Avoid COW during metadata preallocation
Limiting the allocation to INT_MAX bytes isn't particularly clever
because it means that the final cluster will be a partial cluster which
will be completed through a COW operation. This results in unnecessary
data read and write requests which lead to an unwanted non-sparse
filesystem block for metadata preallocation.
Align the maximum allocation size down to the cluster size to avoid this
situation.
Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
| -rw-r--r-- | block/qcow2.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/block/qcow2.c b/block/qcow2.c index 3ace3b2..dfac74c 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2734,7 +2734,7 @@ static int coroutine_fn preallocate_co(BlockDriverState *bs, uint64_t offset, bytes = new_length - offset; while (bytes) { - cur_bytes = MIN(bytes, INT_MAX); + cur_bytes = MIN(bytes, QEMU_ALIGN_DOWN(INT_MAX, s->cluster_size)); ret = qcow2_alloc_cluster_offset(bs, offset, &cur_bytes, &host_offset, &meta); if (ret < 0) { |